Dr. Luis Eduardo Bravo is the Principal Investigator and supervises all activities in Colombia. He is based in Cali and travels often to Pasto. His administrative assistant in Cali is Mr. Tito Collazos who has been the administrator for all the life of the Program Project. Mr. Collazos coordinates the clinical work conducted at Hospital Departamental of Pasto and Hospital San Andres in Tumaco. He also collaborates with Nurse Maria Clara Yepez, in-charge of the children's cohorts at Universidad de Narino. Dr. Bravo's data manager assistant is Mrs. Stella Garcia, who has been in charge of those activities for approximately 10 years and has become extraordinarily skilled and efficient. The data generated in Pasto are entered and edited by Mrs. Alicia Rosero, who also has been conducting these activities very efficiently for years. Mrs. Rosero transmits the data via internet to Nashville and Raleigh, NC for Dr. Robertino Mera. The field team in Narino is under the direction of Dr. Guillermo Zarama, who is also the gastroenterologist and endoscopist in charge. He is based at Hospital Departamental. The field team is based at Universidad de Narino (Pasto) under the direction of Nurse Maria Clara Yepez. She has trained outstanding assistants (nurses-social workers). Mrs. Cristina Campo supervises the clinical nursing and data managing team in Narino. Dr. Juan Carios Bravo is assistant pathologist for gastric biopsies interpretation. The biopsies are fixed and embedded in paraffin in Colombia. A first section is stained and used for diagnostic uses communicated to the clinician. The paraffin blocks are then transported to Nashville for further processing, immunohistochemistry, and other special procedures. RELEVANCE (See instructions): In Colombia there are unique subpopulations, not available in the United States, displaying marked contrasts in terms of risk of gastric cancer and infection with the bacterium Helicobacter pylori, a recognized cause of gastric cancer. The infrastructure to study such populations has been developed over the years and is very efficient.